Does a cover cover a book?

There’s more to a book then words?

 We are trying to put our all onto paper.  But many others have done that before us.They chose a picture on the front, a title, a letter type,….  
They obviously put in a lot of thought or love.
That got me thinking.  Why do we pick a book out of the many choices?  Is it because of a cover, a genre the writer, or the short bit on the back of the book?
Have you ever thought about anything else except your words on the paper?  And what are your thoughts about it.  (That’s still far away, or do you have nightmares about it)  
What leads you to your next (reading) book and do you keep it in the back of your mind when choosing your own materials for your project?